Calculating machine



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CALCULATING MACHINE 8 Sheets-Sheet 2 Original Filed Feb. 18. 1924 FIE.E.

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C. M. F. FRIDEN CALCULATING MACHI NE Original Filed Feb. 18, 1924 8sheets sheet 3 FIE-3.

Sept c. M. F. FRIDEN CALCULATING MACHINE Y 8 Sheets-Sheet 4 OriginalFiled Feb. 18, 1924 0 m Wm x w x w t. 27 1927. 1643 710 sep c. M. F.FRIDEN CALCULATING MACHINE Original Filed Feb. 18, 1924 8 sheets'sheet 5Z m m: WM a Sept. 27, 1927.

c. M. F. FRIDEN CALCULATING MACHINE Original Filed Feb. 18. 1924 8sheets-sheet 6 NWN C. M. F. FRIDEN CALCULATING MACHINE Sept. 27 1927.

Original Filed Feb. 18. 1924 8 sheets'sheet 7 In. l RN to 2 t. 27 1927.c. M. F.'FRIDEN CALCULATING MACHINE Original Filed Feb. 18. 1924 8Sheets-Sheet 8 \um O HTTOE/VEYS Patented Sept--27, 19.27.

CARL M. 1. FRIDEN, OF PIEDMONT,

CALCULATING MACHINE.

CALIFORNIA.

HEISSUED Application filed February 18, 1924. Serial No. 888,546.

The invention relates to calculating machines and particularly tocalculating machines adapted to perform the operations of addition,subtraction, multiplication and di- 5 vision.

An object of the invention is to provide a calculating machine in whichthe multiplication or division of a number by any digit is accomplishedby the depression of a key.

Another object of the invention is to provide a calculating machine inwhich the mental operation involved in the problems of division ormultiplication is completed by the introduction of the digit multiplier1 or divisor into the machine.

Another object of the invention is to provide a calculating machinewhich is automatic in its operation to compute problems involvingdivision and multiplication;

A further object of the invention is to rovide a power drivencalculating machine in which the operation of the machine is initiated,in problems of multiplication and division, by the depression of a digitkey representing one of the factors of the calculation.

A further object of the invention is to provide a universal rotationcontrol mechanism which is adapted. to be operated by either the plus orminus control keys for manually determining the extent and direction ofrotation of the actuator, and by value keys for automaticallypredetermining the number of rotations of the actuator.

A further object of the invention is to rovide, a calculating machinewhich may e operated to add a given number a'plurality of times withoutchanging the setting of the machine.

A further object of the invention is to provide a calculating machinewhich is op erative to perform problems in addition and multiplicationwithout change in the setting of the machine.

A further object of the invention is to rovide a power drivencalculating machine ving means operable during the operation oidivisionto stop the operation of the malchine when the divisor will not go intothe 0 dividend a whole number of times.-

A further object of the invention is to provide a power drivencalculating machine .lprovided with means for disconnecting the Z'Qsource of power from the machine when the 65 machine has completed thecalculating operation.

The invention possesses man other advantageous features, some of which,with the foregoing, willbe set forth at length in the followingdescription, where I shall outline in full, that form of the inventionwhich I have selected for illustration in the drawings accompanying andforming art of the resent specification. In said diawings I ave shownone embodiment of my invention but it is to be understood that I do notlimit myself to such form, since the invention, as set forth in theclaims, may be embodied in a plurality of forms.

it is manifest that the invention comprising the means for automaticallystopping the operation of the calculating machine, after the calculationhas been completed, may be combined with any suitable form ofcalculating mechanism. In the accompanying drawings 1 have shown theinvention embodied in a calculating machine comprismg a countingmechanism actuating device consisting of a rotatable drum in which thevalues to be calculated are introduced, but

it is to be understood that the invention is not limited to use inconnection with a calculating machine having a counting. mechanismactuating device of this character or to a machine having a rotatabledrum for performing the calculating operation. Further, in the machineshown in the drawings, the values are entered into the countingmechanism actuating device by means of a plurality of depresslble keys,but it is to be understood that other suitable or well-known means 131); be employed for introducing the values into the device. It ispreferable, however, to embody the invention in a keyboard calculatingmachine wherein the values are introduced into the machine by thedepression of keys. The calculating machine shown in the accompanyingdrawing is of the true rotary type, embodying a retatable countingmechanism actuator of the reversible cycle type, which is rotated frominitial or neutral stop position through a complete cycle in eitherdirection to perform a calculating operation. The actuator is.rotatedfrom neutral stop position through one or more complete cycles of 360degrees in either direction and is stopped at neutral stop position. Thecounting mechanism is arranged on a carriage, normally stationary withrespect to the actuator, and displaceable longitudinally to make directaction of the actuator on the various figure discs of the countingmechanism possible. The actuator is rotated b an electric motor,preferably continuous y energized durmg the use of the machine, a clutchand stop mechanism being interposed between the motor and the actuator,to permit intermittent rotation of the actuator while the motor operatescontinuously. A reverslng gear is interposed between the actuator andthe clutch to permit rotation of the actuator in either direction.

Referring to said drawings F i ure 1 is a perspective view of one typeof ca culating machine embodying my invention.

Figure 2 is a top or plan view of the machine shown in Figure 1, aportion of the casing being broken away to show the mechanism whichoperates to stop the machine after the selected calculating operationhas been completed.

Figure 3 is a rear view of the machlne shown in Figure 1 with the casingremoved.

Figure 4 is a longitudinal vertical section through the machine showingone bank of keys and the elements associated therewith for entering thevalue to be calculated into the rotatable drum.

Figure 5 is a longitudinal vertical section through the machine showingthe control keys, and the operating mechanism associated therewith forcontrolling the release of the keys for entering the values into the adrum.

Figure 6 is a side elevation of the machine, a portion of the casingbeing broken away to disclose the actuating keys for performing problemsin addition, and subtraction,

' and the mechanism employed for controlling the duration of operationof the machine for solving problems in multiplication and division.

Figure 7 is a detail side elevation of the mechanism for controlling theduration of operation of the machine, the view being taken from the sideof the mechanism opposite to that of which the view in Figure 6 istaken. 7

Figure 8 is a longitudinal vertical section through the machine showingthe keys for predetermining the duration of operation of the machine toperform a calculating operation.

Figure 9 is a cross-section taken on the line 9-9 Figure 8, showing theconstruction of the first key in the series.

Figure 10 is a cross section taken on the line 1010, Figure 8, showing avalue key, the means for holding the key in the de pressed position andthe means for releasing the key at the end of the predeterminedcalculating operation.

Figure 11 is a cross section through the clutch which is interposedbetween the driving shaft and the rotatable drum.

Figure 12 is a cross-section through the machine showing the means forengaging and disengaging the clutch and for centering the drum 1nneutral position.

Figure 13 is a longitudinal section through the counter-shaft, showingthe friction clutch.

Figure 14 is a-detail of a counter mechanism actuating unit inengagement with the counting mechanism.

Fi ure 15 is a side elevation of the cam mem r forming part of anactuating unit.

Figure 16 is a detail of the reversing gear mechanism, the view being asection taken on the line 16-16 Figure 8.

The machine shown in the accompanying drawings is of the keyboard type,in which the values are introduced into the machine by the depression ofkeys. The depression of a key, introduces a value corresponding to thenumeral on the key, into a rotatable drum within the machine, rotationof the drum being efi'ected to accomplish the calculating operation. Thevalues introduced into the drum, are transmitted, on rotation of thedrum, to the figure discs of a counting mechanism, which, for thepurpose of making direct action of the selected values on the figurediscs of highest value possible, is disposed in parallel displaceablerelation to the value selecting mechanism axis.

One of the objects of the present invention is to provide a calculatingmachine in which the mental efl'ort of the operator is finished as soonas the factors of the calculation have been entered into the machine.This is particularly advantageous in a power driven calculating machine,although it may also be used to advantage in a hand operated machine.Calculating machines' have been constructed in the past in which themechanism has been operated by power but in such machines it has beennecessary for the operator to continue to think and to act to stop themachine at the proper time. i

In accordance-with the present invention however, it is not necessaryfor the operator to think, after the factors have been entered into themachine, since the machine will be automatically stopped when thecalculation represented by the factors is completed. Thus, the presentmachine, not only reduces the manual efi'ort necessary to calculationbut greatly reduces the mental effort, the only mental'effort necessaryis that required to insure the proper entry of the factors into themachine.

The calculating machine shown in the drawings, and which embodies thepresent invention comprises a suitable base 22 having side plates 2324,between which the selecting, counting and controlling mechanism devicesare arranged. These devices include a counting mechanism arranged on alongitudinally displaccable carriage, a counting Inn the depressed keyin under the mechanism actuating drum which, upon rotation, causes thevalues entered therein, to become effective in operating the countingmechanism, keys for entering the selected values into the drum, keysfor" determining the duration or extent of rotation of the drum, anindicator for disclosing the values entered into the drum, an indicatorfor disclosing the calculations performed or-being performed and otherdevices for controlling the actuation of the keys, the selectingmechanism, the counting devices, the control devices and otherinstrumentalities. The machine contains all of the elements necessary toquickly and accurately perform the operations of addition, subtraction,multiplication and division and these operations are performedautomatically by the depression of keys. The machine is provided with acover plate disposed between the side plates and arranged on the coverplate,- and preferably towards the left side thereof, are the banks ofkeys which form the keyboard for entering values into the drum. In thepresent illustration, Fig. 1 and Fig. 4, the machine is provided withnine rows of numeral keys each row comprising nine keys numbered from 1to 9 consecutively and also including, at its forward end, a clearancekey 26, depression of which releases the corresponding row. Vhen a keyin a row is depressed, it remains depreJ-Jsed until released, either bythe operation of a clearance key or by the operation of the calculatingmechanism. Extending across the machine, between the side plates 23-24are fixed cross bars .27 and 28 upon which the key sections are mounted,each sec tion con'iprising a row of nine keys 25 an one key 26. Eachsection is formed as a unit and is incorporated in the machine as aunit, and the desired capacity of the machine determines the number ofsections to be employed. Each section comprises a top plate or top strip29, which forms part of the cover plate of the machine. Secured to eachtop strip, adjacent, but spaced from its ends, is a strap 32 which formsa guiding element for the key shanks 33. The keys are normally held inraised positions by springs 34, bearing against the straps 32 an againstthe shoulders formed on the key shanks. Disposed below and the underside of the straps 32is a slide 35 normally held in forward position bythe spring 36. The slide is provided with a plurality of aperturesthrough which the key shanks extend and each key shank is provided witha detent 37, which, when the key is depressed, causes longitudinalmovement of the slide 35 and which engages slide 35, to depressedposition. The clearance key 26 is provided on its face with a projection38, which operates, on depression of the clearin contact with hold thekey in the ancekey, to move the slide to release the depressed key.

I The selecting bar or lever which is variably depressed by thedepression of the dif ferent 'ke s, .is positioned below the stems ancomprises a duplex lever. The main lever 41 is pivoted at its forwardend to a tongue 42 secured to and depending from the frame and isconnected at its free or movable end with a bent lever 46 fulcrumed onthe rod and provided on its other end with a curvedrack 51 meshing witha gear 52 of the counting mechanism actuating device.

Fulcrumed on a tongue 43 positioned between the ends of the lever 41 andnearer the free end thereof, is a secondary lever 44 which is pivoted bythe pin 44 to the main lever 41, the pin being located'adjacent thefulcrum on the tongue 43, 'so that a relatively small angular movementof the pin 44 is produced by a greater angular movement of the lever 44.The lever 44 extends toward the pivoted end of the lever 41 and liesalongside the lever 41. The levers are offset laterally just behind thepin 44', so that the main portion of the lever 44 is alined with therear portion of the main lever 41. The stems of the keys arein alinementand in the present construction, the stems of keys representing thevalues from 1 to 6 inclusive occur directly above the main portion ofthe lever 44, and the stems of keys representing the values 7 to 9inclusive occur'directly above the rear portion of the lever 41. Thus,keys representing the values 1 to 6 inclusive mediately operate the mainlever and keys representing the values 7 to 9 inclusive directly operatethe main lever. When the key representing value4 is depressed, forinstance, it depresses lever 44, thus depressing the free end of thelever 41. When the key representing the value 9 is depressed, itdirectly depresses the free end of the lever 41. By this arrangement, aslight inaccuracy in the length of the key stem or in the amount ofmovement of a key stem, will not produce any material variation in thesetting of the value selecting elements and greater manufacturd. ingtolerances are permissible, thus rendering quantity production possible.

Mounted on the rod 45, disposed at the rear of the machine, are aplurality of levers 46, there being one lever 46 for each key section.Each lever 46 is provided with a horizontal arm connected to the end ofthe 'lever 41 and with a vertical arm connected with the value selectingelement on the counting mechanism actuating drum. The horizontal arm isprovided with a slot 47 which is engaged by a 'pin 48 on the lever 41 topermitrelative movement of the arm and the lever as the lever isdepressed by the numeral keys; Depression of the lever through variouspredetermined distances, causes various angular displacements of thevertical arm 49 of the lever. The vert cal arm 49 is provided on itsupper end with a rack 51 concentric with the rod which 1s in engagementwith a gear 52 on the value selecting element. Depression of a ke in onesection thus causes an angular disp acement of the selecting element 56associated with the section, to a position corresponding to thenumerical value of the depressed key. There is a selecting elementassociated with each key section, in the present instance there beingnine selecting elements. The lever 41 is normally held in raisedposition and the vertical arm 49 of the lever in retracted position by aspring 49 connecting an arm 50 on the lever 46 to the base of themachine.

The counting mechanism actuating drum is mounted on the shaft 53,supported in the side plate .23 and the intermediate 54, Figure 2. Thedrum comprises nine counting mechanism actuating wheels 55, Figures 3and 4, secured to the shaft 53 and nine value selecting elements 56loose on the shaft, a wheel 55 and an element 56 being combined togetherto form an actuating unit. The drum also comprises additional wheels 57,Fig. 3, provided with tens carrying pins and selecting element lockingmeans, as will hereafter be described. The drum is rotatable in eitherdirection from an initial position through a complete revolution back toinitial position by a driving motor which is connected to the drumthrough gearing which is capable of being reversed, so that for rotationof the motor in one directlon, the drum may be rotated in eitherdirection.

Each actuating unit comprises a counting mechanism actuating wheel andan associated value selecting element. The actu ating wheel comprises adisc or wheel carrying a diametrically disposed slide or mem ber 65,Fig. 14, seated in the wheel so that it may be moved diametricallythereof.

The slide is provided on one end withan actuating face provided withnine teeth 66, the teeth being arranged on an are concentric with thewheel and having the same pitch as the teeth of the intermediate wheelof the counting mechanism. The slide is held in the groove in the wheelby a ring 67 secured to the wheel and is normally held in retractedposition with the teeth or curved rack 66 lying within the periphery ofthe wheel. The function of the selecting ele-. ment is to projectorretract -,the slide, at the proper time during the rotation of the drum,to bring the selected number of teeth into engagement with the countingmechanism. The selecting element 56, to 'one side of which the gear 52is secured, is provided on its opposite side, that is, the'side whichlies adjacent the associated actuating wheel, with counting mechanism,when the a cam 68, Fig. 15, which is engaged by a roller 69 on the slide65. Thecam 68 is provided with a high face 1 and when the roller is inengagement with thisface, the slide is held in retracted position, andwith a low face 72, and when the roller is in contact with the low face,the slide is in pro jected position. To insure the positive slidingmovement of the slide, a backing cam 73, complementary to the maincam,is arranged opposite the low {face 72, thus forming a cam groove 74through which the roller travels as the wheel is rotated, thus insuringthe positive slidin motion of the slide at selected times, during therotation of the wheel, depending upon the setting of the selectingelement. The slide is thus reciprocated for each rotation of the wheeland the time of its reciprocation with respect to the position of thewheel, is determined by the setting of the selecting element. When thedrum is rotated in one direction, the slide is projected as theactuating face or rack is passing the intermediate wheel of the countingmechanism, so that the selected number of teeth engage the countingmechanism and is withdrawn after it passes the counting mechanism. Whenthe drum is rotated in the opposite direction, the slide is projectedbefore it reaches the counting mechanism and is withdrawn as soon as theintermediate wheel has moved the selected number of steps. When theselecting elemnt is set at zero, the slide is projected after theactuating face has assed the rum is rotated in one direction and isprojected and Withdrawn before the actuating face reaches the countingmechanism, when the drum is rotated in the opposite direction. Each ofthe nine actuating wheels of the drum is provided with a slide 65 havinga curved rack 66 on its end and in order that allot the projected rackswill not engage the intermediate wheel of the counting mechanism at thesame time, during the rotation of the drum, and thus suddenly throw alarge load on the driving motor, the slides are spaced apart angularlyaround the face of the drum.

Means are provided for indicating the values which have been enteredinto the machine by the depression of the keys, so that itis notnecessary for the operator to search over the keyboard to determine thesetting of the machine. Each selecting element is provided with aflanged rim section 76, Figure 15, upon which the numerals from zero to9 are successively delineated and one immeral in each row on thesuccessive selecting elements is visible through a window 77, Figures 1and 4, in the casing. When a key in a key section is depressed, thenumerical value of the key appears in the window in the positionoccupied by that particular section. Above the window the casing .isprorotation upon the movement of the drum tion. The point at which thelocking from neutral position and for preventing the entering of anyvalues into the drum after it has moved from neutral position. Eachselecting element is provided with an arcuate rack 81 and these racksare engagable by fingers 82, Fi 4, to prevent movement of the selectinge ement when the drum is out of neutral position. The fingers aremounted on a transverse shaft 83, and are connected together to lock orrelease all of the selecting elements. Secured to the sleeve to whichall of the fingers 82 are secured, is an arm 84, Fig; 12,h'aving arounded end engaging the cam. 85- s cured to the drum shaft. The cam isprovided with a de ression 86 which registers with the end 0 the armwhen the drum is in its neutral position, permitting the fingers to fallby gravity from engagement with the racks 81.

Upon movement of the drum, the cam 85 causes 'the arm 84 to' be moved,raising the fingers into engagement with the rack and holding them insuchposition during the time that the drumfl is out of neutral pos1-fingers become effective is determined b the length of the depression86. The va ues entered into the machine by the depression of the keyscan therefore not be altered afterthe drum has moved av predetermineddistance from neutral position. Means are also provided for centeringthe drum in neutral position at the end of each calculating op-'eration. Secured to the drum shaft is a cam 87 havin a dee depression88, which is engaged bye ro'ler 89 on 'the end of the lever 91. he leveris suitabl pivoted within the machine and. the ro er is pressed a ainstthe cam by the spring 92, the slope o the cam and the tension of thespring bein sufiicient to cause the lever to center the rum in neutralposition at the end of a calculating operation.

The calculating machine may be employed to perform operations ofaddition, subtrac-- tion, multiplication and division, a step in anyoperation being performed b a rotation of the drum. Means are provi edfor setting the mechanism to automatically clear the key-board and drumafter each rotation of the drum, when performing problems of addition orsubtraction and for causing the values entered on the keyboard to remainunalterable during successive rotations of the drum, when performing theoperations of multiplication and division. Secured t0 the sleeve tovwhich the fingers 82 are secured, is an arm 93, Fig. 12, which israised when the fi the rack. I cans are rovided f0; lockingthis arm inthe raise position, when the machine is set to perform operations ofmultiplication or division so that the setting mechanism will not bereleased on the rotars are moved into contact with tion'of the drum. Themeans for holding the arm 93 in raised position consists of a lever orabutment 94 which is rocked by movement of the clutch lever 203. Thelever 94 is mounted on the clutch lever shaft 202 and is secured to theclutch lever, so that as the clutch lever is rocked in a clockwisedirection'to cause engagement of the clutch the lever. 94 is moved toengage the raise arm 93 and hold it in such position, thusholdin thedetents 82 in en agement with the rac s 81. Movement of t e clutch leverto cause disengagement of the clutch, rocks lever 94 and t is removesthe stop from below the arm 93, so that the detents are free to fallfrom engagement .with the racks.

During the operations of addition and subtraction, the key-boardisautomatically cleared at each rotation of the drum but- .during. theoperations of multiplication and division, the key-board is notautomatically cleared when the drum moves from neutral position, but iscleared b the use of a clearance key, which will ereafter be described,and which isused after the completion of the multiplying or dividingoperation.

The values entered into the drum, are

transferred, upon rotation thereof, to the.

counting mechanism which is arranged on the longitudinally movablecarriage 95g which is movable to permit the action 0 the actuatingelement on the counting wheels of different value. Any suitable meansare provided for moving the carriage longitudinally either in astep-by-step movement or continuously to either end of its range oftravel. Usually the carriage is moved in a step-by-step movement bymeans of a'lever 96 arranged at the front of the ca:e and mounted on theshaft97 which extends backward to the carriage shifting mechanism 98.Any suitable form of carriage shifting mechanism may be employed and Ihave had successful results with the carriage shifting mechanismshown-in my copending application Serial No. 539,422, filed February 27,1922, to which reference is hereby made for a more complete descriptionof such mechanism. The counting mechanism comprises a plurality offigure discs 101, Fig. 14, arranged in axial alinement in thelongitudinally displaceable carriage. The figure discs are mounted on ashaft and have figures on their faces which are visible throughapertures 99 in-the carriage casing. Each disc is provided onone sidewith a toothed wheel 102, secured thereto, and meshing with an Iintermediate toothed wheel 103 loosely mounted on the shaft 104. Uponrotation of the drum, the toothedfaces of the actuating element moveinto enga ement with the intermediate wheels, causing rotation thereofand consequently rotation of the figure discs. The figure discs areprevented from overthrowing and are caused to move with a step-by-stepmovement b the escapement latches 105, Fig. 4, pivote on the shaft 106.These latches are held in latchin 'engagement with the toothed wheels ofthe counting discs by spring pressed balls 108 carried by the bar 109.The bar'is rotatable to move the balls out of engagement with thelatches and thus free the latches, when it is desirable to reset thefigure discs to zero. Suitable or well-known means may be employed forrotating the figure discs to zero,

y the rotation of the shaft on. which the identified for causing therelease of the latches on the initial movement of the crank 112 so thatthe number discs may be readily returned to zero position. vThe countingmechanism is also provided with suitable transfer levers 113 which 0erate in conjunction with laterally mova le tens-carrying pins on thedrum, to carry over values from one counting disc to the counting discof next higher denomination. Transfer levers and tens-carrying pins ofthe type shown in my copendmg application may e used in the machineshown in the present application and these devices are well known in thecalculating machine art so that it is not necessary herein to describetheir construction or mode of operation.

The machine is provided with means for indicating the third factor ofthe calculation. One factor is indicated by the depression of the valuekeys of the keyboard, the other factor is indicated on the countingmechanism on the carria e and the third factor is indicated indepenently of the first two.

For instance, in the operation of multiplica-' tion, the multiplicand isshown at the window 77, the product is shown on the car riage and themultiplier is shown at the window 109*. This third factor is enteredinto the machine by the rotation of the drum, whichv is rotatable ineither direction as has been set forth hereinbefore. The third factorindicating mechanism is mounted between the side plate 24 and the'intermediate plate 54 and comprises a counting mechanism consisting of aplurality of numeral wheels 114, Fig. 8, each provided on its side witha toothed wheel 115 and meshing with intermediate toothed .wheels 116.The counting wheels are movable with a step-bydiscs are mounted, whichis provided ex-' -ternally e step motion controlled by the springpresseddetents 117. The selected intermediate wheel.

116 is rotated one tooth for each revolution of thedrum by the tooth 118splined to the shaft 119. v The tooth 118 is movable longitudinally ofthe shaft 119 into the plane of theintermediate wheel of the selected donomination by the longitudinal movement an indicator 122, Figures 1 and81, which indicates the denomination of'the numeral being entered intothethird factor. Secured to the collar 120 is a rod 123 which isconnected to the carriage as shown in my copending application so thatthe indicator 122 moves in time with and in the opposite direction tothe carriage. The shaft 119 is rotated by and in time with the rotationof the drum. Rotatably mounted adjacent the numeral wheels 114 is atens-carrying drum 128, this drum being provided with cams 129 andspring pressed pins 131 which cooperate with the transfer levers 132 ofthe counting mechanism to carry 'tens to .the counting wheels of nexthigher denomination. Means are provided for causing the tens-carryingdrum 128 to rotate in either direction for one direction of rotation ofthe value drum, in order to permit the third factor register to be' usedin connection with problems in both multiplication and division.

The drum is driven by an electric motor 135 which is preferably mountedon the base of the machine at the rear portion thereof. The motor shaft136 is suitably journalled in the frame of the machine and is providedwith a flexible coupling 137 to reduce the vibration which ma betransferred from the motor to the mec anism and also to take care. ofany lack of accurate mounting of the 'motor shaft; Secured to the motorshaft is the friction disc is a gear 143. The gears.

139 and 143 and the friction disc 142 are pressed into tight frictionalcontact by the coiled spring 144 surrounding the hollow shaft 141.Thegears 139 and 143 are thus frictionally connected so that normallypower is transmitted from gear 139 to gear 143, but in the event thatgear 143 is held 5, 8, and 16. The gear 149 is movable longitudinally.of the shaft .191 to two different positions to accomplish the reversalof the direction of rotation of the drum with respect to the directionof rotation of the motor. When the machine is being used, the motor isin continuous operation, rotating in one direction, and since it isessential, in performing the different problems in calculation to rotatethe drum in opposite directions, a reversing gear is inserted for thispurpose and the shifting of the gear 149 accomplishes this reversal. Thegear 149 is shifted longitudinally of the shaft 191 by the arm 151 whichengages the collar 148. The arm 151 is secured to the rod 152 whichextends through the hollow shaft 141. At its end, the rod 152 isprovided with a slot in which is disposed the warped or bent arm 153,Fig. 8, of the lever 154 and by shifting the lever 154, the rod 152 ismoved lengthwise to shift the gear 149. The mechanism employed forshifting the lever 154 will be described hereafter.

Journalled on a shaft tel-mediate wall 54 is a and 16, which engagesmounted 'in the inpinion 155, Figs, 3

the gear 149 when such gear is in one of its positions. Secured to ashaft 156 journalled in the intermediate wall 54 is a gear 157 whichengages the gear 149 when said latter gear is in its other position. Thegears 155 and 157 are in mesh with each other so that they always rotatein opposite directions. When the gear 157 is in mesh with the gear 149,such gear 157 rotates in the opposite direction to gear 149.-

lVhen the gear 157 is out of mesh with gear 155 is in mesh with gear149, then gear 157 rotates in the same direction as gear 149. Thereforethe direction of rotation of gear 157 is reversed by shifting1 the gear149. Secured to the shaft 156 an lying on the opposite side oftheintermediate wall is a gear 158 which meshes with a gear 159 journalledon a shaft mounted in ,the intermediate wall and the gear 159 mesheswith the gear 161 which is secured to .the drum shaft. Therefore byshifting the gear 149, the direction of rotation of the drum isreversed. The gears 157, 159 and 161 are of the same diameter and thegear gear 139 may rotate, due to the.

161 is of the same diameter as the gear 157 so that the drum rotates atthe same speed as the gear 157. I

Splined to the shaft of the tens-carrying drum 128 and lying on the sameside of the intermediate wall as the gear 157, is a gear 162 which is ofthe same diameter as the gear 157., The gear 162 is secured to orintegral with a collar 163 which is also slidable on the shaft of thetens-carrying drum 128 so that the gear 162 is movable longitudinally ofthe shaft into engagement with either the gear 157 or the pinion 155. 0When the gear 162 is in mesh with the gear 157, these two gears rotatein opposite direction and when the ear 162 is in mesh with the pinion155, an out of mesh with the gear 157', the gear 157 and the gear 162rotate in the'same direction. Thus, regardless of the direction ofrotation of the calculating drum, the gear 162 may rotate in the samedirection or in the. opposite direction, thus causing the tens-carryingdrum 128, Fig. 3, to rotate in the same or opposite direction. Thecollar 163 is shifted longitudinally of the shaft by an arm 164 securedto the slidable rod 165 which is held in either of its two positions bythe spring pressed ball 166. The rod 165 is provided in its end with aslot which is engaged by the bent or warped end of the lever 167 whichprojects through an aperture in the casing, Figures 1 and 8, so that bymoving the lever 167, the gear 162 is shifted into engagement witheither the gear 157 or the pinion 155, depending upon the desireddirection of rotation of the tenscarrying drum 128. In performingproblems in division it is essential that the tenscarrying drum 128rotate in a direction to show increasing values on the register 114,whereas the main actuator comprising the element 56, must rotate in areverse or subtraction direction. It is therefore necessaryto providemeans of rotation of the tens-carrying drum 128 with respect to theactuator comprising the element 56. The tens carrying drum 128 and theactuating finger 118 may therefore be rotated in the same or 167. Whenthese elements are set to rotate in one direction, the register 114 willshow the number of rotations of the actuator and when set-to rotate inthe opposite direction, the re ister will show the complement of the numer of rotations of the actuator. This feature of the machine, that is,the ability to show the true number or its complement, is of reatadvantage in solving certain arithmetical problems, for instance, whenit is desired to ascertain the number of monthly payments of a fixedamount which must be made to liquidate the purchase price of anarticleplus interest. For instance, the purchase is for $500.00

sition of the lever the opposite 'direction to the actuator dependingupon the po-.

perform many calculating operations with Y a much less number ofoperations of the,

.motor or calculating drum, than has heretofore been possible.

The third factor counter 114 is also advantageously used in determiningmultiplier complements, square roots and in problems in division. Thecounting wheels 114 are readily reset to zero by. rotation of the crank168 secured to the shaft on which the counting wheels are mounted. Anysuitable means, such as is shown in my prior application aboveidentified, may be employe for releasing the latch 117 to permitthecounting wheels 114 to be readily reset to zero position.

Means areprovided for clearing the keyboard and for setting the machineto perform problems in addition and subtraction, the machine beingnormally set to perform problems .in multiplication and division.Arranged on the keyboard are three keys, Figures 1 and 5,. one key 171marked Clear, depression of which clears all inserted values from thekeyboard; another key 172 marked Non-repeat, which, when depressed, setsthe machine for. operations of addition and subtraction, and anotherkey173, marked Repeat, depression of which releases key 172 and restoresthe machine to condition for operations of multiplication and division.The slides 35,which serve to hold. the depressed numeral keys indepressed position, are normally held forward by springs 36 and areprovided on their rear ends with lips 174, Fig. 4. Pivoted to the frameof the machine, and disposed in front. of the lips 174 of the pluralityof slides 35, is a gate or plate 175, which when pushed backward, movesthe slides 35 backward and thus causes. the release of the key-shanks.Pivoted within the casing on a post 176, Fig. 5, is a lever 177, one endof which is disposed below the shank of the key 171. The other end ofthe lever is provided with a cam face 178 which lies adjacent the lower,end of the gate 17 5,

so that depression of the key .171 rocks the gate 17 5 thus moving theslides 35 to release all of the depressed numeral keys.

The devices set into operation by the deression of the key 172, which isheld in depressed position by the spring pressed slide 179 engaging theprojection. 181 on the shank of the key, comprise a tripper bar 182pivoted to the gear 157 so that its free end is reciproeated as the gearis rotated. This gear is directly connected to the calculating mechanism0 rating drum and rotates synchronously t erewith. At its free end, thebar 182 is provided with a rojection 183 which reciprocates back anforth below the gate 175 and normally out of contact with the gate. Thebar 1s supported intermediate its ends and slides on a lateralprojection 184v on the lever 185, pivoted mtermediate its ends to thepost 176. The front end of the lever 185 lies below the shank of the key172 so that when said ke is depressed, the projection 184 is raiseraising the free end of the bar 182 so that the projection engages andswings the ate 175, at each rotation of the gear 157. The depressednumeral ke s are thus released during the rotation o the drum.Depression of the key 172 therefore @causes the depressed keys of thekeyboard to be releasedv during the rotation of the drum and delpressionof the key 173 releases depressed ey 172 and consequently renders thereleasing mechanism inoperative so that the keys of the keyboardrepeated rotations of the drum. These keys may be released by depressionof the clearance key 171. The key 173 cannot be locked in depressedposition and its function is to release key 172. I

The ke s 172 and 173 may be designated as contro keys sincethe'depression of these keys determine the control of the keyboardduring the calculating operation.

lnterposed between the driving shaft 145 and the driving gear 149, is anormally disengaged clutch 147, Figs. 2 and 12, the normal disengagementof this clutch permitting the motor to run continuouslywithout causingrotation of the driving gear 149. The clutch comprises a ratchet wheel188, Fig. 11, secured tothe shaft 145 and a housing 189 secured to theshaft 191 on which the 191 is in axial alinement wit-h the'sliaft 145.Pivoted in the housing 189 is a pawl 192 having a'tooth 193 adapted tobe moved into engagement with the ratchet 188 by the spring 194. Thetooth 193 is normally held out of engagement with the ratchet so thatthe ratchet is free to rotate without causing rotation of the housing.The housing 189 is provided with an aperture 195 through which an ear196 of the awl 192 extends. By pressing the ear 196 inward, the tooth193 is moved from'engagement with the ratchet 188 and means are providedfor normally holding the ear pressed inward so that the pawl is out ofengagement with the ratchet. Whenthe means holding the ear 196depressed, is removed, the pawl drops surrounding collar 148 is splined.The shaft remain depressed during into engagement with the ratchetandremains in enga em'ent until the ear 196 18 again depresse Means arerovided for permitting the engagement an causing the disengagement ofthe clutch for centerm the housing 1n neutral positlon at thedisengagement of the clutch and for preventing improper operation of theclutch. Pivoted 1n the casing on the shaft 202, Fig. 12, disposed belowthe clutch, is a lever 203 having a pro ection 204 on its end which isadapted to en age the ear 196 of the pawl and disengage-t e pawl fromthe ratchet. The lever 203 is normally held in position with theprojection 204 1n contact with the face of the housing 189 by a spring205 connected to the other end of the lever. As the clutch rotates theprojection 204 engages the ear 196 and causes disengagement of theclutch. The clutch is held in neutral position by a lever 206 secured tothe lever 203 and having a cam shaped end 207 adapted to seat in asimilarly shaped depresslon 208 on the face of the housing. The clutchis therefore always stopped in neutral position after disengagement.

Means are provided for preventing the shifting of the ear 149 exce twhen the clutch 1s in neutra position an for reventing rotation of theclutch during t e time that the gear is being shifted. ecured to theclutch housin is a disc 209, Fig. 11, which projects outwar beyond thehousing and which is provided, beyond the periphery of the housin withan aperture or ind entation 212. cured to the arm 151, Fig. 2, whichshifts the ear 149, is a profectlon 213 having a head 214 of substantialy the same shape as the aperture 212. When the housing 189 is inneutral position, the aperture 212 is alined with the head 214 so thatthe head may be moved through the aperture. When the housing is not inneutral osition, the aperture is not alined with the read andconsequently the head may not bemoved through the opening, therebyreventing the gear 149 from being shi ted. Similarly, during the timethat the head 214 is moving through the aperture 212, the housin 189 maynot rotate, due to the presence of the head in the aperture. The meansfor shiftin the gear 149 and the means for ,releasing t e clutch, areoperated by the same instrumentalities and by providing the head 214,the clutch is prevented from rotating before the gear has completed itsIll) shift. In the shifting of the gear, the head moves entirely throughthe aperture in the disc 209 and prevents rotation of the disc as it ismoving through the aperture.

Arranged on the keyboard are two actuating keys 216 -217, Fig. 6. thekey 216 being designated as the addition key and the key 217 beingdesignated as the subtraction key.

Depression of the key 216 causes engagement plurality of times, the gearis not shifted.'

It is understood that depression of the key 216-positions the gear 149in onev osition and depression of the key 217 positions the gear 149 inthe other position. The keys 216 and 217 are normally held in theirraised position by springs 218 and, preferably, the eys are not providedwith means for hold-.

ing-them in the depressed position. Disposed below the-keys 216 and 217is a bracket 219 to which the T-shaped lever 221 is pivoted adjacent itsupper end. One arm 222 of the T-shape'd lever lies under the shankof thekey 216 and the other arm 223 of the T-shaped lever lies under the stemof the key 217. Depression of the key 216 rocks the lever 221to theposition shown in Figure 6 and depression of the key 217 rocks the lever221 to its opposite position. Connected to the lower end of the lever221 is a rod or link 224 which is connected at its other end to thelever 154 which operates to shift the shaft 152. See also Figure 8.Depression of the keys 216 and 217 therefore serve to shift the shaft152 and thus shift the gear 149 to accomplish reverse rotation of thecounting mechanism actuating drum.

Means are also provided for causing the depression of either key 216or'217 to cause engagement of the clutch. Pivoted to the bracket 219adiacent the bottom thereof is ,a late 226 which is rocked backward bythe depression of a key. the plate being normally held in its forwardposition by the spring 227, Figures 2 and 12. The plate is provided.below the shank of the key 216 with a flat surface 228 which is engagedby the shank of the key to cause the plate to rotate about its pivot229. Below the shank of the key 217 the plate 226 is provided with aninclined face 231 which, when it is engaged by the shank of the key,causes the plate to rock backward. The plate is against the tension ofthe spring 205 and this movement, of the lever 203 withdraws theprojectionv 204 from contact with the ear 196 and withdraws the lever206 from the depression 208 thereby permitting engagement of the clutchand rotation of the clutch housing. In accordance with the mechanism sofar described, the clutch will remain in engagement as long as either ofthe keys 216 or 217 is held depressed and as soon as pressure isreleased from the keys, the spring 227, Fig. 6, will pull the lever 232backward and cause the projection 204 on the lever 203 to disengage theclutch and Cause the lever 206 to'stop rotation of the housing inneutral position. Ordinarily, however, the keys 216 and 217 are usedonly to perform problems in addition and subtraction and are not helddown to accomplish problems in multiplication or division. A quickdepression and release of either of the keys will result in thedisengagement of' the clutch after one rotation of the countingmechanism actuating drum, but means have been provided, as will be setforth hereinafter whereby when the control key 172 is depressed.depression of either of the keys 216 or 217 will result only in onecycle of operation of the machine, regardless of the duration of timeduring which these keys 216 or 217 are held depressed. In other words.the machine may be operated to cause continuous rotation of the countingmechanism actuating drum as long as the actuating key is held depressedor may be operated to disengage the clutch after one cycle of operationof the drum. regardless of whether or not the key is held depressed.With the control keys set so that the counting mechanism continues inoperation as long as either of the'actuating keys is held depressed, themachine thus far described may be used in calculating problemsin'multiplication and division but such calculation requires mentaleflort on the part of the operator to count the rotations of the drumand to release the actuating key when the desired number of rotationshave occurred. The machine, how-ever, embodies means which are throwninto actuation by the depression of other value keys to cause the drumto rotate a number of times corresponding to the value of the depressedkey and then cause the machine to function to disengage the clutch sothat the mental effort of the operator is completed by the depression ofthe value key.

' Arranged on the keyboard is another set of value keys 236, Figure 1and Fig. 8, including nine keys numbered from 1 to 9 successively and aclearance key 237 adapted to release any of the depressed keys 236 forthe purpose of correcting an error in the setting or for other purposes.With the motor in operation, the depression of any one of the keys 236will cause the counting mechanism actuating drum to be rotated a numberof tlmes corresponding to the value of the depressed key. That is',depression of the key marked 3 will cause rotation of the drum threetimes and depression of the key marked 8 will cause rotation of the drumeight t mes. At the end of the duration of rotation indicated by thenumeral on the key, the clutch is disengaged and locked in neutralposition. The shanks 238 of the keys 236 are normally held in raisedposition by springs 239 and each shank is provided with a cam-shapedprojection 241, which, when the key is depressed, causes longitudinalmovement of the slide bar 242. The key shanks extend through aperturesin the slide bar 242 so that depression of a key causes a shdingmovement of the .bar. Means are provided for normally holding the slidebar 242 in retracted position and for returning it to such positionafter the release of the depressed key. The depression of a key 236 setsdevices in position to d'etermine the duration of operation of the drum.The engagement of the clutch and the consequent operation of the machinemay be caused by the depression of either of the keys 216 or 217, but Iprefer to connect the series. of keys 236 with the clutch operatingmechanism so that depression of one of the keys 236 will not only set inposition the devices which limit the duration of operation-of the drumbut will also actuate the devices which cause engagement of the clutch.With such arrangement,- it is then only necessary to depress one of thekeys 236 to accomplish multiplication by the number on the depressedkey. The keys 236 may be connected with the clutch control mechanism byconnecting the slide bar 242 with the rocking plate 226, Figure 6, sothat when any key 236 is depressed, the plate 226 is rocked to causeengagement of the clutch. Secured to the end of the slide bar 242 is abracket 243 which s connected to the plate 226 by the rod 244. Thespring 227, see Figure 12, serves to hold the slide bar 242 in retractedposition. When a key 236 is depressed, the slide bar 242 is movedforward and consequently the plate 226 is rocked to move the lever 232to cause engagement of the clutch.

Means are provided for holding the depressed key 236 in depressedposition and for releasing the depressed key after the drum has rotateda number of times corresponding to the value of the depressed key. Whenthe key is released, the wedge 241, Fig. 10, moves from contact with theslide bar 242 and permits the slide bar to be retracted, such retractingmovement being accompanied by a forward movement of the rocPliing plate226, Fig. 6, to neutral position. ach key shank 238 is provided initsside with a notch 245, Fig. 10, which, when the key is drum when thedrum has rotate depressed, is adapted to be engaged by the latchingplate 246. The latch ng plate 246 extends longitudinally alongside thebank of keys 236 and is pivoted at its end on screws 247 set in theframe 248 through which the key shanks 238 extend. By rocking the plate246 about its pivot, the plate is withrawn from the notch in the deresscd key and the key permitted to rise. 'l he key 237 Fig. 9, isprovided on its sidewith a cam face 249 which is engaged by the plate246 and when the ke 237 is depressed, this cam face causes the p ate 246to be rocked sutiiciently to remove it from the notch of the depressedkey. The late 246 is held in contact with the sides 0 the key shanks 238by a spring 252 which exerts an upward pull on the ear 253 whichconstitutes a lateral extension from the lower portion ofthe plate 246.

The plate is therefore sprin pressed against the sides of the shanks ofthe key.

The forward end of the lever 232, Fig. 6, rests on the car 253 and when,by the operation of the limit determining means, the rear end of thelever 232 is raised, the front end of such lever depressesthe'ear 253,rocking the plate 246 about its pivot and releasing the depressed key.When the released key moves upward, the side 242 is retractedandconsequently the rocking plate 226 is moved forward to normal positionby the spring 227. It is the rocking movement of the lever 232 about itspivot on the rocking plate 226 that causes the movement of the plate 246to release the dc ressed key. Below the notch 245, each key siank isprovided with a depression having a slightly inclined upper wall so thatafter the key has been released the rocking plates 246 may be movedbackward by the spring 252 to neutral position.

I shall now describe the means employed in the machine shown in thedrawings for limiting the number of rotations of the counting mechanismactuating drum to the value appearing on the depressed key 236. Thismechanism operates to cause disen gagement of the clutch and stop ing ofthe a number of times corresponding to the value of the depressed key.Associated with the shanks of the keys 236, Fig. 8, and disposed belowsuch shanks is a duplex lever consisting of the main lever 255 pivotedat its forward end to the ear 256 which is disposed adjacent the frontof the machine. Pivoted to an ear 257, preferably arranged adjacent theshank of the eight value key, is a secondary lever 258 which,intermediate its ends, is ivoted to the main lever 255. Theauxiliarylever 258 lies below and is adapted to be engaged by the shanksof the keys 236' representing the values from 1 to 6 inclusive so thatdepression of any of these keys causes downward movement of theauxiliary; lever and corresponding movement of @the main lever 255. Theends of the key shanks are spaced for different distances mm the lever258 so that the lever is moved for different amounts by the depressionof the different keys. The lever 255 is offset adjacent its rear end sothat the rear end 'of such lever lies directly below and is adapted tobe engaged by the shanks of the keys 236 representing the values 7, 8and 9. Depression of either of these ke s causes movement of the lever255 and the (eys are so proportioned that the rear end of the lever 255is moved a. distance corresponding to the value of the de ressed key.The advantages derived by tl'ie use of a duplex lever have been setforth hereinbefore in connection with the duplex levers used with thekeys for entering values into the machine. The movement of the rear endof the lever 255 is em loyed to position a trip actuating device whlchis variably positioned, in accordance with the value of the depressedkey, and I which operates to move the trip to cause disengagement oftheclutch after the drum has rotated a number of times corresponding to thevalue of the depressed key.

, Arranged adjacent the rear portion of the machine is a frame 261,Fig.6, which is secured to the base of the machine. Pivoted to the frame261 adjacent its forward end is a lever 262 which is moved about itsfulcrum by the lever 255. The lever 2621s fulcrumed intermediate itsends on the screw 263 seated in the frame 261 and the V lever 255 isrovided at its rear end with a slot264 in w iich is disposed a pin 265which projects from the rear portion, of the lever .262. The depressionof a key 236 causes downward movement of the rear-end of the lever 255and consequently downward movement of the pin 265 which results inupward movement of the forward portion of the lever 262; This lever isnormall held with its forward portion depressed y the spring 266. Theposition of the forward end of the lever 262 is determined by the valueof the depressed key 236.

Slidably mounted in the frame 261 is a rack bar 267, Fig. 7, which isguided at its forward end by the headed pin 268 which extends throughthe slot 269 in the frame 261. This slot 269 preferably inclines upwardslightly towards the rear of the frame. At its rear end, the rack bar267 is guided by the roller 271. Mounted in the frame 261 above and inmesh with the rack bar 267 is a pinion 272 which is rotated in astep-bystep movement to cause ste -by-step movement of the rack'bar 267.xtending from the side of the clutch housing 189, is a pin 27 3, Fig. 6,which is adapted to engage the pinion 272 and move such pinion one stepfor each rotation of the clutch housing. The rack bar 267 is thereforemoved one step backward for each rotation of the clutch housin Pivotedto the frame 261 above the-rac bar 267 is a latch 274 which may be heldin contact with the teeth of the rack bar 267 by gravity orv by thespring 275. The latch and the rack bar are constructed to permit astep-by-step backward movement of the rackbar and to hold the rack barin its backward position. Means are provided for releasing the latch topermit the rack bar to return to neutral position,

"when the drum has rotated a number of times corresponding to the valueof the depressed key.

Pivoted to the pin 268 which is secured to the rack bar is an arm 276which is provided with an elongated slot 277 in which is disposed thepin 278 which projects laterally from the forward end of the lever 262.The arm 27 6 is thus positioned in variable angular positions, due tothe depression of thevarious value keys 236. The arm 276 is providedwith an ear 281 having a laterally extending pin 282 which operates tocontact with and move the tripping mechanism at substantially the end ofthe last rotation of the counting mechanism actuating drum as determinedby the value of the depressed key 236. The pin 282 is variablypositioned by the depression of the various keys 236 and the movement ofthis pin serves to actuate the tripping mechanism for stopping theoperation of the machine.

Arranged in cooperative relation with the pin 282 is a stepped plate 283which has a limited longitudinal sliding movement on the pins 284 and285 secured to the frame 261.

The plate 283 is normally held in its forward position bythe spring 286connected at one end to the pin 284 secured to the frame an at the otherend to the pin 287 secured to the plate. The forward edge of the plate283 is provided with a series of vertical steps 288, the successivesteps being set backward a distance equal to the length of one step ofmovement of the rack bar267. The front edge of the plate 283 lies in thevertical plane of the pin 282, so that as the pin 282 is moved backwardby the backward movement of the rack bar 267, the pin contacts with thevertical face of one of the steps 288, depending upon the angularposition of the arm 27 6 on which the pin is carried. The steps 288 areso arranged that the pin 282 is moved into contact or approximatecontact with the. vertical face of the step when the machine hascompleted one less than the predetermined number of operations so thatthe final operation or 1:0- tation of the drum will cause the pin tomove the plate 283 backward. When the key 236 representing the value flis depressed, the pin 282 is moved to position in front andsubstantially in contact with the face of the first step 288 so that thefirst rotationv of the drum will cause the movement of the slide plate283 and the release of the clutch.

Means are provided for causing the movement of the slide plate 283 torelease the ward, the upper portion of the lever 291 is moved forward,due to the abutment 292 and this forward movement of the upper portionof the lever is employed to cause the release of the clutch and therelease of the rack bar 267 and the setting mechanism. The lever 291 isprovided on its upper end with an ear 293 which lies in back of andadjacent an ear 294 on the latch 274. As the upper end of the lever 291is moved forward, the ear 293 engages the ear 294, rocking the latch 274about its pivot and releasing the rack bar 267. The rack bar is thenreturned to neutral position by the spring 295 connecting the rear endof the rack bar with the frame 261.

The rear portion of the-lever 232, Fig. 6, lies alongside of the upperportion of the lever .291 and the lever 232 is provided with a laterallyextending pin 296 which lies adjacent to the cam face 297 of the lever291. As the lever 291. is rocked, due to the backward movement of thestepped plate 283,.

the cam face 297 slides under the pin 296 raising the rear end of thelever 232 and raising the lever from engagement with thepin 235 on theend of the clutch control lever. The spring 205, Figure 12, abruptlymoves the clutch control lever to cause disengagement of the clutch andthe lever 206 causes the positioningof the clutch in neutral position.The upward movement of the rear end of the lever 232 by the pin 296,causes downward movement of the front end of the lever 232 causing thelatch plate 246 to be rocked to release the key stems 238. The upwardmovement of the key stems releases the slide plate 242 and permits thespring 227 to move the rock plate 226 back to neutral position. Therelease of the depressed key 236 releases the lever 255 and permits thespring 266 to return the lever 262 to neutral position and consequentlyreturn the lever 276 to neutral posit-ion. These various actions occursubstantially simultaneously so that as soon as the slide plate 283 ismoved by the pin 282,-the machine is stopped and all parts thereofreturned to neutralposition. When the machine is employed to performproblems in addition, subtraction or division, or when it is used toperform problems in multiplication by the use of the plus key 216, thenon-repeat key 172 is in elevated

